The introduction of a gas into a liquid stream is common in many different processing operations. Accordingly, the present invention finds applications in a number of fields such as the treatment of waste and water streams, and disinfecting and clarifying potable water and other fluids. The present invention also finds applications in the food and pharmaceutical industry, as well as industries requiring products that require efficient mass transfer of ozone, air, or other gas for the purpose of flotation, clarification, and/or disinfection. More specifically, the introduction of a gas, such as ozone, air or oxygen, into a liquid stream is common in many disinfecting, treatment and clarifying processes. Very often, ozone is introduced into drinking water sources, ballast water, waste water streams and/or cooling water streams so as to disinfect, treat and/or clarify such liquids due to its superior disinfecting effectiveness over other gases, such as chlorine. Many different methods and techniques have been designed to try and improve the various disinfecting, treatment and clarifying process. When dealing with ozone, additional factors must be considered namely, the unstable nature of the gas which tends to result in higher equipment and operational costs as well as less compact systems. Accordingly, there is a desire to improve the techniques and methods used for introducing, mixing, blending and dissolving a gas into a liquid stream, especially for processes that involve the use of ozone gas.
Canadian Patent Application No. 2,301,583 (Separation Technologies Group PTY. LTD.) discloses a method and apparatus for mixing a first material and a second material, wherein the first material comprises a mixture of two or more dissimilar components that are to be separated. The '583 application discloses the use of a hydrocyclone to mix different materials together prior to their separation. The use of a hydrocyclone in the pre-treatment of the materials to be separated was found to improve the subsequent separation of the materials. The '583 application also discusses the benefits of introducing air or a gas into the mixture of materials to be separated prior to the mixture entering the hydrocyclone. More specifically, the aeration or gasification of the first material facilitates the separation of the dissimilar components in the first material as one of the dissimilar components is entrained or otherwise associated with the air or gas bubbles that are formed from mixing the first and second materials together. It is the formation of millions of tiny gas bubbles that facilitates the subsequent separation of materials as the bubbles entrain or suspend the solid particles or droplets, bringing them to the surface during the subsequent processing steps. The '583 application does not disclose the complete dissolution of a gas within a liquid, as it relies on the formation of gas bubbles within the mixed stream to assist in subsequent separation processes. As well, the system is not necessarily well suited for the dissolution of large amounts of ozone in a liquid stream.
U.S. Pat. No. 6,629,686 (Morse et al.) discloses a process and system for dissolving gas into a liquid at greater concentrations and saturations than previous methods known in the art. A hydrocyclone is used to introduce an intended gas into the liquid stream to be treated. The amount of gas dissolved in the liquid can be optimized by adjusting various parameters of the hydrocyclone, namely by altering the pressure of the incoming liquid, changing the aspect ratio of the inlet, and varying the diameter D and length L of the barrel. Upon exiting the hydrocyclone, the mixed liquid and gas stream enters a diffusion chamber, which converts the radial spin of energized liquid from the hydrocyclone into laminar axial flow. The diffusion chamber is disposed within a pressure chamber, which includes an upper gas region and a lower liquid region. The diffusion chamber is located in the lower liquid region of the pressure chamber so that only large bubbles of undissolved gas coalesce and rise into the gas region of the pressure chamber, while the dissolved gas and micro-size gas bubbles that are retained in the liquid flow with the liquid into the liquid region of the pressure chamber. The gas in the upper region of the pressure chamber is recycled back through the system to the hydrocyclone so that gas is not unnecessarily wasted, and the liquid and dissolved gas mixture can exit the pressure chamber and be held in a storage tank or can be passed along to the next process step in the system. While the '686 patent discloses the use of a pressure chamber, the pressure chamber does not serve as the primary treatment or disinfection vessel. Furthermore, the system does not achieve complete dissolution of the gas into the liquid as it relies on the creation of micro-bubbles to distribute the gas evenly through the liquid.